Catheters, and more particularly, venous access catheters have many very important medical applications. For example, if a patient requires long-term dialysis therapy, a venous access catheter, such as a chronic dialysis catheter, will be implanted in a patient's body. Chronic dialysis catheters typically contain a polyester cuff that is tunneled beneath the skin approximately 3-8 cm and helps to anchor the dialysis catheter to the body. The chronic dialysis catheter is connected to a dialysis machine when the patient is treated. Hemodialysis is a method for removing waste products such as potassium and urea from the blood, such as in the case of renal failure. During hemodialysis, waste products that have accumulated in the blood because of kidney failure are transferred via mass transfer from the blood across a semi permeable dialysis membrane to a balanced salt solution.
In another example, a venous catheter can be used in combination with an implanted port. A port can be implanted in patients that require frequent access to the venous blood, such as chemotherapy patients. An implanted port includes attachment means for fluidly connecting a catheter. The port is implanted in a surgically created pocket within the patient's body and has a reservoir for delivering fluids through the catheter. One end of the catheter is connected to the port, and the other end terminates in a vein near the patient's heart.
Another example of a long-term venous access catheter is a peripherally inserted central catheter, also known as a PICC line. PICC lines are placed in patients requiring long-term access for the purpose of blood sampling and infusion of therapeutic agents including chemotherapeutic drugs.
Notwithstanding the importance of venous catheters, one problem that is associated with their use is the undesired formation of fibrin sheaths along the catheter wall. See, for example, Savader, et al., Treatment of Hemodialysis Catheter-associated Fibrin Sheaths by rt-PA Infusion: Critical Analysis of 124 Procedures, J. Vasc. Interv. Radiol. 2001; 12:711-715. Fibrin sheath formation is an insidious problem that can plague essentially all central venous catheters. It has been reported that fibrin sheath formation occurred as early as 24 hours after catheter placement and that this phenomenon was seen on 100% of central venous catheters in 55 patients at the time of autopsy.
The growth of a fibrin sheath along a catheter shaft can prevent high flow rates, adversely affect blood sampling and infusion of chemotherapeutic drugs, and provide an environment in which bacteria can grow, which may result in infections. Despite fibrin sheath build up, infused fluids may still enter the blood circulation, but when negative pressure is applied, the fibrin sheath can be drawn into the catheter, occluding its tip, thereby preventing aspiration. Complete encasement of the catheter tip in a fibrin sheath may cause persistent withdrawal occlusion. This can lead to extravasation of fluid where fluid enters the catheter to flow into the fibrin sheath, backtracks along the outside of the catheter, and exits out of the venous entry point and into the tissue. The presence of a fibrin sheath on the catheter shaft may also result in difficulty removing the venous catheter, particularly PICC lines, from the patient.
Often patients who need prolonged intravenous regimens have compromised peripheral venous access and thus venous catheters are often the only means available for the delivery of necessary treatment. Therefore, such venous catheters should be configured to remain in a patient so that drugs and other fluids can be effectively delivered to the patient's vasculature and to break up any fibrin sheath growth.
There are a number of different techniques that have been developed to address the fibrin sheath-impaired venous access catheter. These techniques include new catheter placement, catheter exchange over a guide wire, percutaneous fibrin sheath stripping, and thrombolytic therapy. For example, fibrin sheaths may be removed by mechanical disruption or stripping with a guidewire or loop snare, or by replacing the catheter. Mechanical disruption can help prevent the need to replace the catheter, and thereby eliminate disruption to the patient. However, mechanical disruption may not be effective because the fibrin sheath may not be completely removed and often causes damage to the catheter shaft and vessel wall. Mechanical removal of fibrin build-up may also increase the risk of embolism due to free floating debris within the vessel.
Replacing the catheter is also an option, but this can cause increased trauma to the patient, increased procedure time and costs, increased risks of pulmonary emboli, and may require numerous attempts before removal is successful. Thus, both mechanical disruption and catheter replacement may adversely affect a patient's dialysis schedule, cause patient discomfort, and loss of the original access site. Drug therapies that address the fibrin sheaths can also result in complications and are unreliable.
Therefore, it is desirable to provide a device and method for the destruction of undesirable cellular growth on a venous catheter in a safe, easy, and reliable manner without having to remove the catheter from the patient and without damaging the vein or catheter itself.